Ok... Merlot helped a lot
Yes, it was the AVR. My previous checks were not thorough enough.
Its toast.
I must stop wearing nylon underpants and stroking the cat while building projects
Seriously though, Im surprised. the kit was in a zerostat bag when bought, it only came out of the bag onto my equipotential mat and assembly followed normal(ish!) ESD routine... OK I wasnt wearing my wrist strap, but iron, mat and all assembly kit including the "helping hands" are equipot. This is the first one Ive smoked thru static. My real job has me handling stuff thats a) much more ESD sensitive and b) just a tad more expensive to replace. Its not usually a problem here. The Atmega series are usually all but bomb proof.
I shall chalk this one up to "one of those unexplained things"... and stop wearing nylon underpants... (the cat hides whenever Im building something now)